The present invention relates to a turbine housing of an exhaust-gas turbocharger.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Combustion engines, in particular for use in motor vehicles, are increasingly charged using turbo machines so as to improve efficiency while maintaining engine capacity. As a result, the performance can be increased or less fuel is consumed and thus less CO2 emission is produced while maintaining the performance.
In engine development, a supercharging machine or a turbo machine, in particular a turbocharger, is suited to the power characteristics of a motor at hand. In order for the turbocharger to operate at high efficiency, exact gap dimensions of individual structural parts have to be maintained before, during and after operation. Temperature differences of up to several 100° C. are encountered between various operating conditions, causing the various structural parts and used materials as well as material thicknesses to undergo expansions which deviate from one another. In the event of an expansion, gap dimensions change between the individual structural parts so that the presence of an unwanted blow-by effect within the turbocharger may be encountered. This adversely affects efficiency. In addition, structural parts may come into contact with one another as a result of different expansions. In a worst case scenario, the structural parts collide, causing damage or a total breakdown of the turbocharger.
Another important factor in automobile construction relates to weight which should be reduced for all materials and components. Manufacturers strive therefore to optimize weight for a turbocharger, in particular of the turbocharger housing in sheet-metal construction, so as to be able to optimize weight during production of an exhaust-gas turbocharger.
German Pat. No. DE 100 22 052 A1 proposes a decoupling of exhaust-conducting components and supporting and sealing outer structures. While the exhaust-conducting components of a turbocharger are exposed to high thermal stress and thus glow during operation, the thermal stress on the sealing outer structure is markedly less. However, also the outer housing is subject to very high thermal stress and flow-based stress especially in the regions of attachment onto the bearing case of a turbocharger and also at the inflow sides of the relatively hot exhausts.
The inner housing normally rests against the bearing flanges or is additionally coupled with the bearing flanges by a material joint. When the inner housing rests on the bearing flanges, different thermal expansion coefficients may cause leakage and thus may cause a blow-by. When implementing a coupling through a material joint, the heat impact zone of the thermal joining process is weakened in terms of geometry and material as a consequence of the thermal joining process. This region may encounter crack formation and thus also fatigue fracture or leakage under extreme stress conditions or during the operating life of a turbocharger.
It would be desirable and advantageous to provide an improved exhaust-gas turbocharger to obviate prior art shortcomings.